[stuarttaylor00]

Hi guys, long time reader, first time poster.

I currently have a Shapeoko 3 desktop machine, this is my first router, and was a good introduction into CNC routers. However I've outgrown mostly the work area, but also the production capability - I'd like to be producing more parts, and be able to knock out decent parts from 6061 aluminium.

The house I am renting now only has a small shed, so I am limited to a 1000x1500 bed area, but I would like the option in future to go to a full sheet size, or 1200x2400 work area, without having to make too many changes. This is the reason I Have gone the full width machine at a shorter length. I know people say this design is flawed but I think it is robust enough to deal with it. and it means I can just buy longer 8080 y rails and more base supports

For the drawing I have sourced all my extrusion from Misumi Singapore - I am based in Australia and this is the cheapest, closest option for heavy extrusions.

Extrusion sizes are:
gantry - HFS 160x80
risers - HFS 80x80
Y-axis rails - HFS 80x80
Base supports - 40x80
Plates - 10mm 6061

Risers will also be bolted to the gantry with the 8020 anchor - same type as the CNCrouterparts guys use on their machines.

Linear bearings are Hiwin HGR20 all round - with dual blocks on each side of the Z-axis, with the rail mounted on the extrusion, and blocks mounted on the x-carriage - A more detailed drawing is in the works.
X&Y Drive will be by 15mm widthHDT(or similar) belt
Z drive will be a ballscrew of some sort, or even ACME thread with delrin nut (I have been told this is a decent option)


electrics are:
This G540 & 387oz-in stepper kit - http://www.homanndesigns.com/index.p...products_id=67
2.2kw chinese spindle (no specific type)




I guess I'm just after some input on the design. I have never designed a cnc router before so don't know which way is best. My design takes a few ideas from the CNCrouterparts machine, and also the 3dtek 'heavy mill'.
After the shapeoko I want to get away from delrin V-wheels. I don't mind the belt drive, but am unsure how it will go driving a heavier gantry around. The back of the X carriage is incomplete so far, but will have the Z drive shaft-up with a closed belt to the ballscrew shaft. the X drive will sift on the carriage shaft down running the belt to the ends of the gantry.

There will be more supports on the base, as well as a 15x180 type T-slot bed. I'm just trying to nut out the basic design at this stage. On that note, the Hiwin rails arent drawn in, but the bearing blocks are - and drawn to correct size to get clearances right.


Please try and be constructive, I have read too many posts where people just say "this is a stupid design that will never work, engineering fancy words blah blah" without offering any advice. This isn't what I'm after, I have seen some great builds on here, and know there is a lot of knowledge around. Please share it with me, without shooting down my first try at a router design.




cheers guys

[gfacer2]

I'm no designer but the Z looks a little high for good rigidity compared to the rest of the design. But that's based strictly on appearance.

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[justindewoody]

I think it looks great. With regard to the last comment about the Z looking a little too high...I thought the same thing about my design...but in the end it all worked out fine. I have a tall Z as well, but there are no rigidity issues (or any other issues) whatsoever. As long as build it nice and sturdy, you should be fine. And you are only machining materials up to 6061 aluminum (not steel), so I think you are good to go. Great design.

Here's a few pics of my machine...

[ger21]

I think the gantry is definitely too tall. Unless you need the height, it looks like it's twice as tall as you need to.
15mm belts will have a lot of flex. If your goal is to cut aluminum well, use ballscrews.

[stuarttaylor00]

Thanks for the input guys, much appreciated.

justindewoody: - your design looks great! looks so solid. maybe I should look at putting my Hiwin rails on top of the Y-rails instead of the outside, I was trying to keep them out of the way of any debris. That will give me a bit more room for the drive, whether it is belting or ballscrew.
- You have used thicker aluminium then I did, what thickness is it? I thought 10mm would be enough but maybe I should go a little thicker. Where did you source your ballscrews from? What was the price? what size are your linear rails?

ger21: - I Had thought that maybe it was a little tall, currently from the bottom of the gantry carriage to the top of the wasteboard is 300mm. maybe I could knock 100mm off that? I don't want less than 200mm of working height, as my shapeoko only has 100mm and it causes me a few issues with material height + tool length often being more than 100mm. Where do you imagine the high height would cause issue? could I make it stronger in that area?

- I have tossed up between belts and ballscrews a bit. I have been warned off cheap ballscrews as being more trouble than they're worth. This machine isn't high budget, so I can't afford industrial quality ballscrews, maybe you could point me in the direction of some decent quality ones on ebay/aliexpress?

cheers

[justindewoody]

- your design looks great! looks so solid. maybe I should look at putting my Hiwin rails on top of the Y-rails instead of the outside, I was trying to keep them out of the way of any debris. That will give me a bit more room for the drive, whether it is belting or ballscrew.
- You have used thicker aluminium then I did, what thickness is it? I thought 10mm would be enough but maybe I should go a little thicker. Where did you source your ballscrews from? What was the price? what size are your linear rails?

I used mostly 3/4" Mic 6 aluminum. There are a few small pieces of 1/2" and 3/8" as well. But the vast majority is 3/4" Mic 6. I had my ballscrews custom machined by Chai at linearmotionbearings2008 on Ebay. I paid less than $200 for all 4 custom machined RM2005 ballscrews with ballnuts...delivered. That is one HELL of a deal. And they showed up at my door in about 10 days...from China. They were a small investment compared to all the other parts and pieces to my machine. The linear rails/bearings were a big expense and the 80/20 extrusions were a big expense.

[ger21]

my shapeoko only has 100mm and it causes me a few issues with material height + tool length often being more than 100mm

You make the Z axis able to lift the tool to clear the bottom of the gantry, and you don't have that issue. You're gantry only needs to clear the material. I would say you want a gantry clearance of no more than 150-200mm. I'd lean towards 150mm, unless you know you'll be putting something taller than that under it.


The taller you make it, the less rigid it becomes. The Z axis acts like a lever, and the taller the gantry is, the taller the lever becomes. Cutting forces that are transferred to the gantry are magnified as height increases. I would say that unless you are mounting a vise or rotary axis to the table, it's unlikely that you would ever really use more than 100mm of gantry clearance, if the machine is designed correctly.

Check out BST Automation on Aliexpress.

[stuarttaylor00]

That's a good point, I will make a few modifications to lower the gantry and ensure I have that clearance so the tool can be clear of the bottom of the gantry.

I have a few other questions about the design..

- Linear bearings on the outside(as per pics) or on top of y rails?
- are 387oz NEMA24s suitable?
- Is the design of the gantry risers suitable? I took a few cues from the CNCRP machines, as it looked simple and strong.
- what diameter and pitch ballscrew would suit the machine, and those steppers? Ideally I want a balance between being able to cut at high-ish speeds, but still be able to do some aluminium work. I have realistic expectations about what can be achieved with aluminium and a gantry-type router, but would still like to be able to cut new parts for routers etc.

Thankyou for your input, much appreciated

[ger21]

I have a few other questions about the design..

- Linear bearings on the outside(as per pics) or on top of y rails?

Doesn't really make any difference.

- are 387oz NEMA24s suitable?

Probably?

- Is the design of the gantry risers suitable? I took a few cues from the CNCRP machines, as it looked simple and strong.

No. The blue part should be much thicker. Are they 10mm? They look thinner. Also, the bearing blocks should be spread apart a little more. And the black plates tying the uprights to the risers should probably be thicker as well. Angles would be better than flat bars. You could wrap the angle around the sides.

- what diameter and pitch ballscrew would suit the machine, and those steppers? Ideally I want a balance between being able to cut at high-ish speeds, but still be able to do some aluminium work. I have realistic expectations about what can be achieved with aluminium and a gantry-type router, but would still like to be able to cut new parts for routers etc.

I would say 2010 screws are what you would want.

[stuarttaylor00]

Awesome, this is exactly the info I need - I have looked at a lot of designs on here and other areas, but still don't really know which areas need to be stronger and which areas don't require it.
the blue and black plates are both 10mm, I think they look slim because they are bolted to an 8080 extrusion. I've bumped them up to 16mm, and dropped the Z height to 200mm from bottom of the gantry to base... Thoughts?

*edit* Could I just put another strap on the outside of the riser? or is there a lot of strength to be gained from using a piece of angle?
and should the gantry ballscrew run between the two linear bearings? or could it run directly above the top linear bearing?

[wizard]

Awesome, this is exactly the info I need - I have looked at a lot of designs on here and other areas, but still don't really know which areas need to be stronger and which areas don't require it.

It really helps to understand your expectations are because this makes a big difference in what will be acceptable to you. To put it bluntly this design would not meet my expectations if I was focused on machining aluminum. A greater focus on stiffness is needed. However since we don't know what your expectations are we can't say if this design will do for you.

In any even look towards the weakest links in the design. In this case I have concerns about the gantry supports and the X axis bearings. This especially if you maintain the high Z.

I'd also think seriously about a steel gantry beam and uprights. If you eventually follow through on making a longer machine you will have made a solid investment. The only bad thing here is that you need access to a machine shop to do such a gantry beam well.

the blue and black plates are both 10mm, I think they look slim because they are bolted to an 8080 extrusion. I've bumped them up to 16mm, and dropped the Z height to 200mm from bottom of the gantry to base... Thoughts?

The whole arrangement of the verticals may need rethinking if you are very space constrained. Normally I like simple arrangement of components but this will result in a bit of ""wasted space"" behind the gantry. This gets even worst if you spread Out the X axis linear bear blocks. Only you know how much space there is in your shed. Even so you loose travel equal to the bearing spread on your X - axis.

*edit* Could I just put another strap on the outside of the riser? or is there a lot of strength to be gained from using a piece of angle?

You may want to study 80/20 or Mitsumis design guides but I tend to favor an excess of reinforcement when using extrusions. Things do loosen up if the joints are free to rock.

and should the gantry ballscrew run between the two linear bearings? or could it run directly above the top linear bearing?

Ideally between the bearings.

A couple of observations:

1. If you expect to do a lot of aluminum plan on coolants / lubricants.
2. Ball screws or acme screws are pretty much a requirement to do aluminum well. Ball screws should be considered the better choice if anti backlash.
3. As others have mentioned be sure you really need the Z height. This has a dramatic impact on how much torque is applied to the gantry and vertical supports. If you need that clearance you have to make sure those components can resist the torque.

[gfacer2]

That looks more rigid to my untrained eye. My last machine had 8" under the gantry max and it was never an issue in 6 years. I think the most I used was about 3.5 inches cutting a hole in an existing ballistics rated prison window.

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[dmalicky]

Good advice from Gerry, as usual. Your design looks clean and easy to make. Good choice of big tubular extrusions rather than plates for the structure. (Keep in mind extrusions are not as stiff as standard tubes, but of course they are easier to work with.) And good layout of the Y and Z bearings. The desired stiffness depends on what you want to machine and how aggressively. I'd guess this machine would cut wood fine, and alum with pretty light cuts.

For high Z designs like this, it's best to space the X bearings apart a little further to prevent tipping deflection.

For packaging layout, you may want to move the gantry rearwards so the spindle can cut more of the table. I.e., redesign the blue pieces so when the spindle is mounted, the cutter can reach further to the back of the table. That will require the blue plate to be even thicker to effectively tie to the front X bearings.

You probably know that the black straps from riser to gantry will reduce your Y travel. If thick enough, they should be reasonably stiff for this type of design, since they connect large areas of each face. But an added angle on the inside corner would help, as would a plate on the far outside surfaces (i.e., full perimeter connection).

Yes, run the Y ballscrew between the Y bearings -- that is much stiffer than driving it from the top of the gantry.

[pippin88]

Will Misumi Singapore sell to you easily? When I looked a few years ago they only wanted large business customers, registering to purchase was a nightmare, and they only did FOB (got the goods to their local port) and would not arrange door to door. All very different from US Misumi.

I ended up using AME systems in Melbourne. Best I found in Australia.

[stuarttaylor00]

dmalicky - Thanks for the kinds words - Simple is what I am going for. I will look at moving the risers to the back of the blue plate, that is a good point.


Wizard - you're right, I wasn't as clear as I could have been about my needs and expectations.

The majority of my work will be wood: relief carvings, sign work\V carving, and general cutting of wood designs.
My expectations for aluminium are not high - this machine won't be doing aly work day in\day out. My shapeoko 3 cuts 6061 aluminium in .2mm DOC at 800mm/min, with pretty decent accuracy (i would say within .05mm on the part), if I can improve on that - great, if I can only match it - then that is also acceptable. I would imagine making something a bit more solid like this will increase the DOC I can take while keeping a bit of accuracy, the Shapeoko has a pretty flimsy Z axis and still manages ok.

At this stage I'd like to stick with the extrusion gantry, but am thinking of moving to steel risers. Are there any designs you think I would be wise to follow with the risers? or just wing it as I have with the rest of the design?
I'm thinking I could replace the blue plates and black straps with 10mm or 1/2" steel plate.

I'm currently away from my computer but am thinking of making a steel plate that will bolt to the end of the gantry, and also bolt to the bearing blocks (as the current blue plate does), with some steel angle, or box section welded or bolted to the outside of it for support. would I need to have these parts skimmed flat at a machine shop to keep them straight enough for the bearing blocks? I'm unsure about welding the angle or box section to the plate, I'd like to keep it pretty straight.

What is the best grade of steel to use? I don't know what's available at a machine shop in small quantities like this, but the money I save on materials will pay for getting them skimmed.

pippin88 - I had no issues registering with misumi, I just used my ABN and business name (I used to repair pumps in the oil and gas industry, but haven't used it for a few years), and I can get quotes online for the extrusion shipped to my door with DHL or Fedex. Shipping is brutal for one piece of extrusion, but it doesn't increase much as you add more pieces. I was looking at around AU$800 shipping included for the extrusion required for this design. I will investigate AME though, always happier buying from aussie guys

[hanermo]

Any steel will work.
All are equally rigid.

All are not equally strong, but you wont be approaching strength, as loading will be approx 2% of "strength".

Thicker and bigger is better, in this case.

[justindewoody]

I forgot to mention the size of my linear rails/bearings. I used the HGR25 rail with the HGH25 bearings. I did not want to use the wide flanged bearings (HGW25), but you can use them with the same HGR25 rail. I found a killer deal on Ebay for the rails/bearings. There's a guy on there who acquired a big lot of rails/bearings from a business closing down...or something like that. They are all brand spankin' new. I got (2) 711mm rails, (2) 530mm rails, (2) 1308mm rails, and (12) bearings blocks...for $779...delivered. That's even better than buying from China. In fact, this is the very best deal I could find anywhere. This guy is in Canada and his Ebay user name is kbautomationsupply.

[G59]

I forgot to mention the size of my linear rails/bearings. I used the HGR25 rail with the HGH25 bearings. I did not want to use the wide flanged bearings (HGW25), but you can use them with the same HGR25 rail. I found a killer deal on Ebay for the rails/bearings. There's a guy on there who acquired a big lot of rails/bearings from a business closing down...or something like that. They are all brand spankin' new. I got (2) 711mm rails, (2) 530mm rails, (2) 1308mm rails, and (12) bearings blocks...for $779...delivered. That's even better than buying from China. In fact, this is the very best deal I could find anywhere. This guy is in Canada and his Ebay user name is kbautomationsupply.

At the current exchange rate, it's definitely the best deal around. Wow how did I miss that one.

[stuarttaylor00]

I used 12mm plates in a similar arrangement, but I used two spaced apart by solid aluminium bar. My profiles are 9090 heavy type, twice as thick as standard so you may not need to make it so substantial. See images. I can literally ride this thing while it's cutting and it has no effect on the cut. Yes I tried.

Thanks for that, I was thinking around 12mm would be right, if I struggle with flex I can always beef it up\ make a new one.

You can build a far superior Z axis for a lot less money than the $600 for theirs. And if you bought theirs, it would be the weakest part of the machine.

A Z axis with linear rails is about as simple as it gets. Basically all you need is two 3/4" aluminum plates.
$150 for the rails:
Aliexpress.com : Buy 100% New Original HIWIN Linear Guide HGR20 L300mm Rail + 2pcsHGH20CA Narrow Carriages for CNC Router from Reliable carriage link suppliers on BST AUTOMATION | Alibaba Group

$80 for the ballscrew:
Aliexpress.com : Buy Free Shipping 1605 Ball screw RM1605 L 300mm Ballscrew + SFU1605 Ballnut + BK12 BF12 + 1605 Ball nut Housing + Coupler from Reliable coupler cable suppliers on BST AUTOMATION | Alibaba Group

If the screw doesn't fit, you can either remove some material from the center of the two plates, or add some bar stock under the rails to increase clearance.
Depending on where the nut mounts, you can probably get away without using the bottom ballscrew bearing, which simplifies things quite a bit.

Excellent info, thankyou! I think I'll go with this option.

A few questions:
- 3/4" aluminium plate on both plates?
- If 3/4" is to be used, do I need any bracing on either of the plates to stop flex, or should it be OK?
- Is there any reason to have the bottom bearing on the Z ballscrew? i.e would it make a noticeable difference leaving it off?
- just to confirm on the bearing block mounting on the carriage: wider mounting is better on X axis, taller is better on Z axis?

Thanks for the input gents

[stuarttaylor00]

So I've made a few updates. I've beefed up the rear strap from the gantry to the riser, and changed the design of the Y plates. I have changed the material of the bracing plates to 10mm Steel.

I've also widened the bearing blocks on the Carriage, which means I've had to remove the brace on the front of the riser to the gantry. Looking at it now I could probably put a brace only half the width so I still get Y travel to the end of the bed